In various embodiments, a traveling wave amplifier circuit is disclosed. The traveling wave amplifier circuit is configured to receive an RF wave and an electron beam. The traveling wave amplifier effects synchronized interaction between the RF wave and the electron beam. The traveling wave amplifier circuit comprises a waveguide. The waveguide comprises a plurality of asymmetric cells arranged periodically. The waveguide is configured to receive an electron beam. Each of the asymmetric cells comprises at least one asymmetrical structure within the asymmetric cell to modify the dispersion relation of the waveguide.